1. Field of the Invention
The present invention relates to dielectric waveguide nonreciprocal circuit devices and radio devices using the same.
2. Description of the Related Art
Conventional circulators using nonradiative dielectric waveguides (hereinafter referred to as NRD waveguides) have been disclosed in Japanese Unexamined Patent Publication No. 8-181509, Japanese Unexamined Patent Publication No. 9-181506, and Japanese Unexamined Patent Publication No. 9-186507.
FIG. 11 shows the basic structure of a circulator using the above NRD waveguide. In FIG. 11, reference numerals 1 and 2 show an upper conductive plate and a lower conductive plate, respectively. Three dielectric strips indicated by reference numerals 3, 4, and 5 are disposed between the two conductive plates 1 and 2 to form NRD waveguide. Magnetic members 6 and 7 are disposed at positions where the three dielectric strips 3, 4, and 5 approach each other. Magnets 8 and 9 are disposed at positions on approach sides of the magnetic members 6 and 7. The upper and lower conductive plates 1 and 2 are disposed between the magnetic member 6 and the magnet 8 and between the magnetic member 7 and the magnet 9, respectively. With this arrangement, a DC bias magnetic field is applied. The DC magnetic field is applied to the magnetic members 6 and 7 in directions vertical to the surfaces of the magnetic members 6 and 7, and a magnetic field component of a high frequency parallel to the DC magnetic field is applied. In this situation, due to the ferrimagnetic characteristics of the magnetic members 6 and 7, the planes of polarization rotate and the circulator functions.
In a dielectric waveguide nonreciprocal circuit device such as the above circulator, it is important to make a structure in which magnetic members are supported while being disposed in specified positional relationships with a plurality of dielectric strips extending in different directions.
Japanese Unexamined Patent Publication No. 8-181509 and Japanese Unexamined Patent Publication No. 9-181506 each describe a circulator having a supporting member of a ring configuration or a cylindrical configuration. Japanese Unexamined Patent Publication No. 9-186507 describes a circulator in which the structure for supporting magnetic members is arranged on the dielectric strips by providing stepped portions at the edges of the dielectric strips.
The example shown in FIG. 11 uses the dielectric strips 3, 4, and 5, which are discrete components. However, as shown in FIGS. 12A and 12B, it is also possible to use a structure in which three dielectric strips 3, 4, and 5 are integrated with a supporting member for supporting magnetic members 6 and 7. In each of FIGS. 12A and 12B, reference numeral 10 denotes the supporting member, which is integrated with the dielectric strips 3, 4, and 5, for supporting the magnetic members 6 and 7.
However, the inventors of the present invention have investigated and discovered that, with the supporting member having a ring or cylindrical configuration, due to an influence of the dielectric constant of the supporting member, the insertion loss and reflection loss characteristics deteriorate, which causes a problem of degrading the nonreciprocal characteristics of the device.
Accordingly, it is an object of the present invention to provide a dielectric nonreciprocal circuit device capable of obtaining excellent nonreciprocal characteristics by improving the structure of a portion supporting a magnetic member, and to provide a radio device, incorporating the same.
As will be described below, in embodiments of this invention a supporting member for supporting the magnetic member has almost no influence on the nonreciprocal characteristics of the device, based on an analytical result which has determined that the electromagnetic field distribution is concentrated in a portion where the magnetic member is in contact with the dielectric strips and in portions near an upper conductive plate and a lower conductive plate.
According to one aspect of the present invention, there is provided a dielectric waveguide nonreciprocal circuit device including a magnetic member, a supporting member for supporting the magnetic member, an upper conductive plate and a lower conductive plate, and dielectric strips disposed in radial directions with respect to the magnetic member at the center of the arrangement, the dielectric strips disposed between the upper and lower conductive plates. In this structure, the supporting member is formed in such a way that the supporting member supports the magnetic member at locations other than where the magnetic member is abutted against the dielectric strips and where the magnetic member is disposed in close proximity to the dielectric strips.
With this arrangement, since no parts of the supporting member for supporting the magnetic member are provided where the magnetic member is in contact with the dielectric strips, which is a place where an electromagnetic field distribution is concentrated, the influence of the supporting member is reduced.
In addition, in the above dielectric waveguide nonreciprocal circuit device, edges or corners of the adjacent dielectric strips are connected to each other by the supporting member.
In addition, in the dielectric waveguide nonreciprocal circuit device described in the first aspect of the present invention, the magnetic member may be supported by the adjacent edges or corners of the dielectric strips, and the side walls of the dielectric strips may be connected to each other by a connecting member made of a dielectric material.
Furthermore, the magnetic member may be supported by the connecting member.
According to another aspect of the present invention, there is provided a radio device incorporating one of the above-described dielectric waveguide nonreciprocal circuit devices as a circulator formed by the dielectric transmission lines comprising dielectric strips. The circulator propagates a transmission signal and a reception signal, and performs branching of the transmission and reception signals.
According to another aspect of the present invention, there is provided a radio device incorporating an isolator formed by providing a terminating member on a predetermined dielectric transmission line comprising one of the dielectric strips in one of the above dielectric waveguide nonreciprocal circuit devices. The isolator blocks a reverse-propagation signal.